1.7\ Doppler Spectrum

of the External Carotid Artery

Fig. 7.7  Doppler spectrum of the external carotid artery

1.7.1\ Scanning Method

The subject takes a supine position with the head slightly stretched to make a full extension of the neck. The probe is placed on the posterolateral neck behind the sternocleidomastoid and the sound beam directly from the anteromedial to the sternocleidomastoid muscle. The longitudinal section of the bifurcation of the common carotid artery is shown, and scanning is performed from bottom to top. The internal carotid artery is located posterolateral to the neck; the external carotid artery is located anteromedial to the neck. The pulse-Doppler sampling volume is placed in the middle of the artery, and the Doppler beam correction angle θ line parallels to the beam flow line as far as possible; the angle should be no more than 60.

1.7.2\ Section Structure

low diastolic flow velocity; its resistance index is higher than that of internal carotid artery.

1.7.3\ Measurement Methods

Measuring the peak velocity and resistance index of the blood flow spectrum.

1.7.4\ Clinical Significance

The spectrum morphology, blood flow velocity, and resistance index (RI) of the carotid artery can be used to distinguish the internal carotid artery from the external carotid artery. There is another indicator that differentiates ICA from ECA: when one taps the temporal artery in front of the ear, the Doppler spectrum of the external carotid artery has small repeated fluctuation peaks, while there is no fluctuation in Doppler spectrum of the internal carotid artery.

1.8.1\ Scanning Method

The subject takes a supine position with the head slightly stretched to make a full extension of the neck. The probe is located at the root of the neck scan. For the deep carotid artery, the initial section of the clavicle, and the aortic arch, use the 3–5 MHz low-frequency probe to scan.

1.8.2\ Sectional Structure

Left carotid root longitudinal scanning displayed a longitudinal section of the partial aortic arch, the initial segments of the left subclavian artery and the left common carotid.

1.8.3\ Measurement Methods

Measuring the diameter and the blood flow spectrum of the initial segments of the left carotid artery and the left clavicle.

1.8.4\ Clinical Significance

Showing the anatomical location, situation of the wall and lumen of the carotid artery, subclavian artery, and aortic arch; tracking the subclavian artery or innominate artery stenosis and occlusion lesions when measuring blood flow spectrum to diagnose subclavian steal syndrome.